In a process of converting, for example, cellulose-based biomass to bioethanol or the like by fermenting saccharides obtained by operations such as pretreatment and enzymatic saccharification, methods in which pretreatment is performed under high-temperature and high-pressure conditions have been considered. Implementing such pretreatment requires a means that stably and continuously feeds biomass, which is a solid with low bulk density (for example, 0.05 kg/L), into a reaction device that is under high temperature and high pressure (for example, not less than 1.0 MPa).
As that means, it has been proposed that, for example, a slurry pump, a piston pump, a screw feeder, or the like be used (Patent Document 1).